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q-bio.NC · Neurons and Cognition

SEEG word-encoding memory effect shows no left-hemisphere advantage in 11 bilateral RAM FR1 subjects when epochs use correct sample timing (HFA, theta, tilt; paired sign-flip, Holm p = 1.0)

We tested whether the subsequent memory effect (SME) in stereo-electroencephalography (SEEG) bipolar pairs was larger in the left hemisphere, using correctly timed per-word features from the RAM FR1 task (26 subjects; OpenNeuro ds004789, session 0). Epoch time was sample/fs, from 0 to 1.6 s after word onset. We assigned pair hemisphere from the mean MNI x coordinate of its contacts in the dataset electrodes.tsv files. For each pair and feature, the SME was the Welch t statistic comparing recalled with not-recalled words. The primary test compared left and right subject-mean pair t values in 11 bilateral subjects with at least 3 pairs per side, using an exact sign-flip test and Holm correction over HFA, theta, and tilt. The left-minus-right differences were HFA +0.230 (95% CI -0.203 to 0.662, p = 0.334), theta +0.178 (95% CI -0.364 to 0.721, p = 0.524), and tilt +0.043 (95% CI -0.492 to 0.577, p = 0.890); Holm-adjusted p = 1.0 for all three. Although the left-pair HFA SME was positive in 19 subjects (mean t = 0.395, p = 0.0062), the right-pair HFA SME was not significant in 16 subjects (mean t = 0.056, p = 0.61), and this difference in significance is not a significant left-right difference. The left HFA SME was also not significant after removing serial-position effects (p = 0.29) or within the same 11 bilateral subjects (p = 0.12). Theta decrease and tilt increase occurred on both sides. These findings provide no evidence of a larger left-hemisphere SME with correctly timed features, consistent with earlier onset-timed null results. The bilateral sample is small; the HFA confidence interval permits a left advantage up to about 0.66 t units, and electrode coverage differed between sides.

stereo-electroencephalography · subsequent memory effect · hemispheric lateralization · word encoding · RAM FR1 · HFA · theta · sign-flip test

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References

4
  1. supportsHFA and theta subsequent memory effects were not larger on the left in 53 pure-SEEG patients sci:sha256:9063d3f2e90c6671c1f514ca61635883687a496bee8044caa831e8f0ed1f1805

    Its paired left-right null in bilateral subjects used onset-timed features; the null also holds with correctly timed features.

  2. supportsA 72-subject SEEG subset showed no leftward HFA memory effect; leftward theta effects remained exploratory sci:sha256:a05eb03d61033b87ece75cef1dc09f58392bde85530843f547a706c1bc484c72

    It found no significant left-right SME difference; this result agrees for all SEEG pairs with correctly timed features.

  3. supportsIn 71 pure-SEEG patients, left-hemisphere 70–150 Hz memory effects were null and pair effects matched chance (FR1, session 0) sci:sha256:b16337b0615008397830d1f15010d2fd40c8f95101740a6c57846fe22277b0bb

    Its lateralization null used onset-timed features; the null also holds with correctly timed features.

  4. usesAssuming sample/fs marks EDF time, 21 pure-SEEG FR1 patients showed a subsequent memory effect hidden by onset timing sci:sha256:799055dd0e8b95498bb3ea5d9564670cf779d6970c9993bda2f0c41150b419e7

    Uses the correctly timed features_sample per-word band power and ports its SME method; the port reproduces its per-subject HFA values.

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